Gaseous tube selecting switch for use in automatic telephony



K. KAELL GASEOUS TUBE SELECT ET AL ING SWITCH FOR USE IN AUTOMATIC TELEPHONY Filed Dec.

May 27, 1952 Patented May 27, 1952 GASEOUS TUBE SELECTING SWITCH FOR USE IN AUTOMATIC TELEPHONY Knut Kaell and Erik Waldemar Hullegard, Stockholm, Sweden, assignors to Telefonaktiebolaget L M Ericsson, Stockholm, Sweden, a company of Sweden Application December 23, 1947, Serial No. 793,352 In Sweden January 3, 1947 Claims. (Cl. 179-18) This invention relates to a selector device of the gaseous discharge tube for closing a circuit across any one of a selected pair of contacts to connect the calling to the called line in a telephone system.

The selector device of the present invention is particularly adapted for use in a telephone system. Similar selector devices of more general application are described and illustrated in the co-pending application of Erik Waldemar Hullegard, one of the joint inventors herein, Serial No. 784,485, filed November 6, 1947.

A selector device of this kind herein concerned comprises a gaseous discharge tube containing two electrodes, an anode and a cathode, between which a gas discharge can be produced by connecting them to different poles of a current source and which are so arranged within the envelope of the gaseous discharge tube, that an arc discharge shaped as a string, outside Which only an unimportant ionization of the gas is obtained, can be maintained between them when they are connected to the current source. Said tube contains moreover an arbitrary number of other electrodes, contact electrodes, to which the arc discharge can be directed by actuation from electromagnetic means, for instance, a coil arranged outside the tube envelope in order to deflect the path for the discharge.

The present invention concerns more particularly a circuit arrangement for a gaseous discharge tube of the kind referred to and its principal object is to provide means for precisely defining the zero position of the arc discharge within said tube.. The arrangement comprises a device for automatic setting of the initial or zero position of the arc in such tubes, thus giving the arc discharge a fixed zero position, from which it will start the movement to the different contact electrodes. Such a fixed initial position of the arc discharge is suitable partly because the arc can obtain a central initial position in relation to the difierent electrodes, and partly because an initial position, not exactly determined, may affect the operations of the device in an unfavorable manner.

Another object of the invention is to provide an improved switching device for automatic telecommunication systems including telephone sets and the like.

According to the invention the tube is provided with one or more electrodes, hereinafter called centering electrodes, which are so arranged within the envelope that they will be influenced by the arc, when this is brought to the zero position.

Thus it may be of advantage to place the centering electrodes in the middle of the tube, that is, centrally in relation to the contact electrodes, or in one end of the tube. The contact-electrodes are so arranged that the arc discharge is ignited at a satisfactory distance from the centering electrodes. The current in the field coil generating the magnetic field for controlling the arc discharge is altered so that the arc discharge will move in a direction towards the centering electrodes. When these are touched by the arc discharge, a circuit will be actuated over the centering electrodes in such a way, that the arc discharge stops at these electrodes, that is, the mentioned alteration of the circuit for controlling the current intensity in the coil and consequently the strength of the magnetic field generated by said coil is decreased to zero.

The invention is clearly illustrated in the accompanying drawing in which the figure is a circuit diagram according to the present invention showing in particular a gaseous discharge tube comprising an arrangement of electrodes for completing a circuit from a common electrode to a selected electrode of a plurality of individual electrodes.

An embodiment of the device described above shown in the annexed drawing wherein the envelope of the discharge tube is indicated by l, the electrodes for the discharge are by 2 and 3, wherein 2 is the anode and 3 the cathode, and the difierent contact electrodes 8, of which ten are shown in the figure, and a common counterelectrode 3|. The electrodes 8 and the common counterelectrode 3| are connected in the circuits to the called telephones.

A pair of centering electrodes 32 are so arranged in relation to each other, that a local arc discharge easily can be be produced between them, if they are connected to a suitable current source and the arc discharge I3 is caused to touch them. One electrode is connected to one (positive) pole 33 of a current source and the second over the winding 34 of a relay R2 and a contact 35 of a relay BI is connected to the other (nega tive) pole 36 of the same current source. The functions of the relays will be described more fully below.

The field coil M, the object of which is to generate a variable magnetic field for shifting the arc discharge 13 into different positions within the tube (crossing diiferent contact electrodes 8), obtains its current from a current source between the positive pole I6 and a zero pole l5 over an electron tube 31, the anode-current of which is controlled by means of a grid 38 which is normally connected to a source of voltage 39 over a contact spring 48 on the relay RI, said voltage being negative in relation to the pole IE, to which the cathode or the tube is connected. The cathode connection at O is positive with respect to the terminals marked and negative with respect to the terminals marked The grid i further in series with a condenser 51 connected to one side of the winding 42 of relay RI. The other side 43 of the winding is connected to a source of negative voltage, which is negative in relation to the pole l5. To the first mentioned side of the winding 42 of the relay RI a number of telephone sets are connected via a line finder 49. On the drawing only two telephones sets 44 and d8 are shown but the other sets are represented by series of conductors 59 and Bi connecting them with the line finder 59.. The telephone set M is connected to uppermost conductor 55 and the set 48 to the uppermost conductor 55. Other sets (not shown) would be connected successively to the next lower conductor in theseries.

In the position of the relays shown in the drawing, the voltage on the grid 8 has such a selected value, that only a small anode current passes through the tube. Upon initiation of calls from one of the telephone sets the relay RI is attracted over a circuit established from the pole over the line finder 59, line and hook contact (not shown) of the telephone set, line 50 and the winding 52 of relay R1 to the negative pole 53. Thus contact $5 is closed and an arc discharge between the electrodes 2 and 3 is started. The are current passes through a resistance of appropriate value. Further the contact is thrown to the opposite position, so that the grid is connected to zero earth potential (the cathode potential) in series with a resistance 46. The grid voltage will thus rise at a rate substantially dependent on a time constant de termined by the condenser M and the resistance 46. The anode current, that is, the current through the coil i4 rises, with the result that the just ignited arc will be moved in a direction towards the centering electrodes 32.

When these electrodes are touched by the arc discharge, a local discharge is ignited between them. Current flows through the winding 34 of the relay R2 and the contact 47 opens, the increase of the grid voltage is interrupted and the movement of the arc discharge is consequently brought to a stop and the latter remains in the position it has reached, that is, in the position where it touches the pair of centering electrodes 32. makes contact from the common counter electrode 34 to one of the electrodes 8 to complete circuit to the called line.

The telephone sets are provided with push buttons as indicated in the set 44, by means of which different resistances i? by means of which different resistances may be connected to the conductor 56 or M to provide pulses of varying intensities over these conductors. This set of push buttons functions in the same manner as the dial in a dial telephone. The resistances are connected in series with the winding c2 of relay RI, with the result that the voltage across said winding 42 will be varied according to the voltage drop over the connected resistance. Said voltage is brought to the grid of the electron tube 87 across the condenser 41. The anode current of this tube and thus the strength of the field generated by the coil it are varied and the discharge The are I3 in its various selected positions arc is forced to move within the tube I and is arrested in a certain position in said tube, which position is determined by the field strength of the coil i4 depending on the resistance I? connected to one of the conductors in the series iii in the telephone sets, in the same manner as described in the copending application Serial No. 784,485.

The resistances l1 shown in the telephone set 48 are of relatively unequal ohm values and these values are determined in such a way that every resistance connected to one of the conductors in the series 51 gives rise to a current intensity in coil [4- of a certain predetermined value. Each of said resistances corresponds accordingly to a predetermined strength of the field influencing the position of the arc discharge within the tube and also to a predetermined position of said discharge within said tube. It is, in other words, possible to direct the arc discharge to a certain electrode 8 in the tube by connecting a corresponding resistance I! in the telephone sets to the calling line. As moreover the initial-position of the arc discharged is precisely determined by the circuit arrangement described above it isobvious that an improved selector device is obtained.

Alternatively to the now described device with control of the field current in the magnet coil of the tube, the position of the arc may be controlled 'by means of variation of the arc current at a fixed coil current. Combinations of both methods may be of course also possible, for instance, there may be one or two or more different initial positions for the arc discharge selected by means of variation of one magnitude, while the are discharge is directed to different contact electrodes of acontact group belonging to this initial posiion by means of variation of the other magnitude.

We claim:

1. A circuit arrangement for a gaseous discharge tube, which Within an envelope comprises an anode and a cathode connectable to difierent poles of a current source for producing a string shaped are between said anode and cathode, an arbitrary number of pairs of contact electrodes between said anode and cathode across any pair of which the arc discharge may complete a current path and a pair of centering electrodes across which the arc discharge may extend, said contact electrodes and said centering electrodes each consisting of two plates mounted in spaced relation, said arrangement comprising means for generating a magnetic field within said tube, means for changing the force of said magnetic field in order to move said string shaped are discharge within said tube and to direct the same to any one of said pairs of contact electrodes, said last mentioned means comprising an electron tube controlling the current through said means for generating a magnetic field, and means for stopping the variation of the force of said magnetic field in order to arrest the movement of said string shaped are immediately upon its touching each of said pairs of centering elecrodes.

2. A circuit arrangement for a gaseous discharge tube, which within an envelope comprises an anode and a cathode connectable to different poles of a current source for producing a string shaped arc discharge between them, a set of contact electrodes being between said anode and cathode, a common counterelectrode arrangedto be electrically connected to any one of saidcontact-electrodes by said are discharge and a pair of centering electrodes consisting of two plates mounted adjacent each other and across which the arc discharge may extend, said arrangement comprising means for generating a magnetic field within said tube, means for changing the force of. said magnetic field in order to move said string shaped arc discharge within said tube and to direct the same to any one of said contact electrodes, said last mentioned means comprising an electron tube controlling the current through said means for generating a magnetic field, and means for stopping the variation of the force of said magnetic field in order to arrest the movement of said string shaped are immediately upon its touchingsaid centering electrode.

3. A circuit arrangement as claimed in claim '2, wherein said means for generating a magnetic field comprises a coil.

4. A circuit arrangement for a gaseous discharge tube, which within an envelope comprises an anode and a cathode connectable to different poles of a current source for producing a string shaped arc discharge between them, an arbitrary number of contact electrodes between said anode and cathode across which said are discharge may complete a current path and a pair of centering electrodes across which the arc discharge may extend, said arrangement comprising a coil for generating a magnetic field within said tube, means for changing the force of said -magnetic field in order to move said string shaped arc discharge within said tube and to direct the same to any one of said contact electrodes, said last mentioned means comprising a grid-controlled electron tube, the anode of which is connected to said coil, means for varying the anode current of said electron tube and means connecting the grid controlling circuit of-said electron tube to said pair of centering electrodes, said grid controllin circuit being arranged to stop the variation of the anode current of said tube in order to maintain the current through said coil at a fixed value and consequently to arrest the movement of said string shaped are discharge immediately upon its touching said centering electrode.

5. A circuit arrangement for a gaseous discharge tube, which within an envelope comprises an anode and a cathode connectable to different poles of a current source for producing a string shaped arc discharge between them, an arbitrary number of contact electrodes between said anode and cathode and a pair of centering electrodes across which the arc discharge may extend, said arrangement comprising a coil for generating a magnetic field within said tube, means for chan ing the force of said magnetic field in order to move said string shaped arc discharge within said tube and to direct the same to any one of said contact electrodes, said last mentioned means comprising a grid-controlled electron tube, the anode of which is connected to said coil, means for varying the anode current of said electron tube, a relay in series with the centering electrode arranged to operate on short-circuiting of said electrode and a break contact in the grid controlling circuit of said electron tube arranged to be actuated on the operation of said relay, said grid controlling circuit being arranged to stop the variation of the anode current of said tube on the actuation of said break contact in order to maintain said current at a fixed value, and consequently to arrest the movement of said string shaped are discharge on the connection of said centering electrodes by the last mentioned are discharge connection of said centering electrodes by the last mentioned arc discharge.

6. A circuit arrangement for a gaseous discharge tube, which within an envelope comprises an anode and a cathode connectable to different poles of a current source for producing a string shaped arc discharge between them, a set of contact electrodes between said anode and cathode, a common counterelectrode arranged to be-electrically connected to any one of said contactelectrodes by said are discharge and a pair of centering electrodes arranged to be connected by said are discharge, said arrangement comprising a coil for generating a magnetic field within said tube, means for changing the force of said magnetic field in order to move said string shaped arc discharge within said tube and to direct the same to any one of said contact electrodes, said last mentioned means comprising a grid-controlled electron tube, the anode of which i connected to said coil, means for varying the anode current of said electron tube, a relay in series with the centering electrodesarranged to operate on connection of said-electrodes, and a break contact in the grid controlling circuit of said electron tube arranged to be actuated on the operation of said relay, said grid controlling circuit being arranged to stop the variation of the anode current of said tube on the actuation of said break contact in order to maintain said current ata fixed'value and consequently to arrest the movement of said string shaped arc discharge on the connection of said centering electrodes by said arc discharge.

7. In an automatic telecommunication system utilizing telephone sets and the like, a switching device comprising in combination a gaseous discharge tube, which within an envelope comprises an anode and acathode connectable to diiferent poles of a current source for producing a string shaped arc discharge between them, a set of contact electrodes, a common counterelectrode arranged to be electrically connected to any one of said contact electrodes by said are discharge and a pair of centering electrodes arranged to be connected by said arc discharge, said device comprising a coil for generating a magnetic field within said tube, a grid controlled electron tube, the anode of which is connected to said coil so'as to feed said coil with current from said tube, circuit elements arranged to be connected to the grid of said electron tube in response to calls from a telephone set, said circuit elements producing a continuous alteration of the grid voltage of said tube in order to vary the current through said coil and consequently to move said string shaped arc discharge; within said tube, a relay in series with said centering electrodes arranged to operate on the connection of the same, and a break contact in the grid controlling circuit of said electron tube aranged to be actuated on the operation of said relay, said grid controlling circuit being arranged to interrupt the alteration of the grid voltage on the actuation of said break contact so as to maintain said current through said coil at a fixed value and thereby arrest the movement of said string shaped arc discharge as soon as it touches said centering electrodes.

8. In an automatic telecommunication system utilizing-telephone sets and the like, a switching device comprising in combination a gaseous discharge tube, which within an envelope comprises an anode and a cathode connectable to different poles of a current source for producing a string shaped arc discharge between them, a set of contact electrodes. 2. common counterelectrode arranged to be electrically connected to any one of said contact electrodesby said are discharge and a. pair of centering electrodes arranged to be connected by said are discharge, said device comprising. a coil for generating a magnetic field within said tube, a grid controlled electron tube. the anode of which is connected to said coil so as to feed said coil with current from said tube. a condenser connected to the grid of said electron tube, a calling relay in series with said condenser, a contact appertaining to said relay connected to. said. grid in parallel with said condenser and relay and arranged to be actuated on the actuation of. said relay in response to calls from a telephone set, said contact and said relay being connected to a negative voltage giving the electron tube and said coil a suitable initial current, another contact appertaining to said relay-andarranged to connect said grid to another voltage over a resistance in response to calls from a. telephone set in order to change the grid voltage of said tube with a time constant determined by said condenser and the resistance in the grid circuit and to produce a continuous alteration of the anode current from said tube through said coil and consequently to move said string shaped arc discharge within said tube, a second relay in series with said centering electrodes arranged to operate on connection of the same, and a break contact in the grid controlling circuit of said electron tube arranged to be actuated on the operation of said second relay and operable thereupon for disconnecting said grid from said resistance and said voltage so as to interrupt the alteration of the grid voltage and maintain said current through said coil at a fixed value, and consequently arrest the movementof said string shaped arc discharge as soon as it touches said centering electrodes.

9. In an automatic telecommunication system with telephone sets and the like, a switching device eomprising in combination a gaseous discharge tube, which within an envelope comprises an anode and a cathode connectable to difierent poles of a current source for producing a string shaped arc discharge between them, a set of contact electrodes, at common counterelectrode arrangedto be electrically connected to any one of said contact electrodes by said are discharge and a pair of centering electrodes arranged to :be connected by. said are discharge, said device comprising,- means for generating a magnetic field within said tube and means for changing the force ofsaid magnetic field inorder to direct said string shaped arc discharge within said tube to any. oneof said contact electrodes, said last mentioned means including a series of difierent resistances in each telephone set, which resistances are connectable to the telephone line for controlling the current through said means for generating a magnetic field, means producing a continuous return movement of said are discharge and means for stopping said return movement as soon as said arc discharge touches said pair .of centering electrodes.

10. In an automatic telecomunmication system with telephone sets and the like, a switching device comprising in combination a gaseous discharge tube, which within an envelope comprises an anode and a cathode connectable to different poles of a current source for producing a string shaped arc discharge between them, a set of contact electrodes, a common counterelectrode arranged to be electrically connected to any one of said contact electrodes by said are discharge and a pair of centering electrodes arranged to be connected by said are discharge, said device comprising a coil for generating a magnetic field within said tube, means for changing the forceof said magnetic field in order to move said string shaped arc discharge within said tube and to direct the same to any one of said contact electrodes, said last mentioned means comprisin a grid-controlled electron tube, the anode of which is connected to said coil so as to feed said coil with current from said tube, means for varying the anode current of said electron tube, a relay in series with said centering electrodes arranged to operate on short circuiting of the same, a break contact in the grid controlling circuit of said electron tube arranged to be actuated on the operation of said relay, said grid controlling circuit being arranged to interrupt the alteration of the grid voltage on the actuation of said break contact in order to maintain said current through said coil at a fixed value and consequently to arrest the movement of said string shaped are discharge as soon as it touches said centering electrodes, and a series of setting resistances in each telephone set, which resistances. for the purpose of selecting are connectable to the telephone line for controlling the current through said coil and directing said are discharge to a contact electrode corresponding to the setting; resistance connected to said telephone line at the same moment.

KNUT KAELL. ERIK WALDEMAR HULLEGARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,122,102 Lundell June 28, 1938 2,204,055 Skellett June 11, 1940 2,339,684 Deakin Jan. 18, 1944 

